1. Field of the Invention
The present disclosure relates to a shape measurement apparatus and a shape measurement method.
2. Description of the Related Art
There is an apparatus, for example, that illuminates laser light onto an object surface and receives laser light that is reflected from the object surface to thereby execute non-contact measurement of the three dimensional shape of the object. Japanese Patent No. 4375710 discloses this type of shape measurement device in a configuration of a three dimensional measurement apparatus that is provided with a galvanized mirror as a light flux deflection mechanism that is configured to radially deflect and scan laser light, that is illuminated towards the object surface, from a reference point. On the other hand, from the point of view of avoiding a change in measurement accuracy, a spot diameter of the laser light flux that is illuminated onto the object surface preferably exhibits the small possible fluctuation amount even when the position on the object surface changes. Therefore, Japanese Patent Application Laid-Open No. 2010-51983 discloses a manufacturing apparatus for a solid circuit substrate in which the spot diameter of the laser light flux on the object surface is fixed and a focus adjustment lens is disposed in a probe to thereby adjust a focal point of the laser light flux.
Since a radial scan with the laser light flux is executed by the light flux deflection mechanism in the three dimensional measurement apparatus disclosed in Japanese Patent No. 4375710, the incidence angle of the laser light flux onto the detected surface (object surface) changes in response to the position on the detected surface. Therefore, there is the possibility of an measurement error resulting from the spectral pattern (interference fringe) produced on a coarse detected surface, or by an amount of reflected light from a detected surface that changes in response to the incidence angle. The measurement error also changes as a result of the incidence position of the laser light flux on the detected surface. Furthermore, since the position of the beam waist of the laser light flux (distance from the distance measurement meter to the beam waist) is fixed, the spot diameter changes in response to the distance between the detected surface and the distance measurement meter. In particular, when the spot diameter on the detected surface is fixed, a deterioration in the amplitude that results from an averaging effect on the coarse component or the wave-shaped component on the detected surface can be corrected. In this regard, when the spot diameter changes, the spot diameter is adjusted to a fixed range by provision of a focal adjustment lens in the probe as adopted in the manufacturing apparatus disclosed in Japanese Patent Application Laid-Open No. 2010-51983. However, the increase in the probe size in this configuration causes an increase in the overall size of the shape measurement apparatus.